Tracks such as as those on endless track laying tractors comprise a large number of individual links joined to each other. Each link is provided at each end with structure that enables it to be joined to the succeeding link. The two ends of each link are different from each other to provide a series of such linkages. The links are arranged in pairs on opposite sides of the track.
Heavy oil or, perhaps grease in some structures, is used to provide lubrication at the places where pins cross transversely between a pair of link ends and also join each pair of links to the succeeding pair of links, for at that linkage, the adjacent links can rotate somewhat relative to each other. The rotation is limited to considerably less than one hundred eighty degrees but does involve a certain amount of rotary reciprocation and wear of the bushing against the drive sprocket of the track.
Adjacent each end of each transverse pin is a lubricant sealing member. It lies between a first link end and a bushing that, in effect, is part of a second link end. The rotary seal is between the bushing and the first link end. There is also a static seal against the first link end and the pin, which is tightly press-fitted to the first link end. The sealing member provided by the original equipment manufacturer may be part of an assembly that includes a two-element sealing member and a spacer ring. In some cases a one-element sealing member may be used, and the spacer ring may in some instances comprise part of a unitary sealing member.
As indicated above, a portion of the sealing member provides static seals with the circumference of the pin and with the first link end, for the first link end and the pin, being connected together by a press-fit arrangement, comprise, for operational purposes, a single piece. The first link end provides a recess in which the sealing member or assembly are seated. The second link end and its accompanying bushing, also being fitted together by a press fit, also act as a unit; the bushing provides a radial face against which a lip of the sealing member abuts to provide the rotary seal for retaining the lubricant inside the overall assembly.
During operation, a portion of the periphery of the bushing is gradually worn down by its engagement of the drive sprocket during reciprocating rotary movement; however, since the motion is reciprocating and never reaches 180.degree., it is possible to repair the track linkage by removing the bushings and inverting them, so that the wearing surface against the drive sprocket is again a cylindrical arc.
However, the sealing member has simultaneously been worn out and required replacement. More significantly, it has also worn the bushing so that there there is an annular groove in the end face of the bushing. This groove tends to frustrate reinstallation. If a new seal arrangement of the original type is put in, the lubricant will immediately begin leaking from the linkage, because the new seal will not make firm contact with the face of the bushing, due to the annular groove, which is of substantial depth. Machining off of the faces of the bushings is not practical, for that would worsen the situation.
One object of the present invention is to provide for improved repair by a combination which includes a type of lubricant sealing member which is markedly different from that originally supplied. This different type of lubricant sealing member has a lip which runs on a different portion of the face, spaced away from the annular groove that has been worn into the face by the original sealing member. This new type of sealing member is suitable for use over a period even longer than the life of the original sealing member. Moreover, if the new sealing member itself wears, it can easily be replaced.
The alternative to such repair in which only the seal is replaced, is a replacement of the entire bushing at each link end. This can be very expensive since each track includes a number of these seals and bushings, typically about 80 bushings and 160 seals.
Another object of the invention, therefore, is to make possible reworking of the worn installation by mere inversion of the bushings and replacement of the seals, so that it will not be necessary to replace each bushing during the repair work.
Another object of the invention is to provide for relatively inexpensive repair requiring only inversion of the bushing and a new sealing member.